package com.icloud.framework.interceptor;

import java.io.Serializable;

import net.sf.ehcache.Cache;
import net.sf.ehcache.Element;

import org.aopalliance.intercept.MethodInterceptor;
import org.aopalliance.intercept.MethodInvocation;
import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
import org.springframework.beans.factory.InitializingBean;
import org.springframework.util.Assert;

public class MethodCacheInterceptor implements MethodInterceptor,
		InitializingBean {
	private static final Log logger = LogFactory
			.getLog(MethodCacheInterceptor.class);
	private Cache cache;

	/**
	 * 设置缓存名
	 */
	public void setCache(Cache cache) {
		this.cache = cache;
	}

	/**
	 * 检查是否提供必要参数。
	 */
	public void afterPropertiesSet() throws Exception {
		Assert.notNull(cache,
				"A cache is required. Use setCache(Cache) to provide one.");
	}

	/**
	 * 主方法 如果某方法可被缓存就缓存其结果 方法结果必须是可序列化的(serializable)
	 */
	public Object invoke(MethodInvocation invocation) throws Throwable {
		String targetName = invocation.getThis().getClass().getName();
		String methodName = invocation.getMethod().getName();
		Object[] arguments = invocation.getArguments();
		Object result;
		logger.debug("looking for method result in cache");
		String cacheKey = getCacheKey(targetName, methodName, arguments);
		Element element = cache.get(cacheKey);
		if (element == null) {
			// call target/sub-interceptor
			logger.debug("calling intercepted method");
			result = invocation.proceed();
			// cache method result
			logger.debug("caching result");
			element = new Element(cacheKey, (Serializable) result);
			cache.put(element);
		}
		return element.getObjectValue();
	}

	/**
	 * creates cache key: targetName.methodName.argument0.argument1...
	 */
	private String getCacheKey(String targetName, String methodName,
			Object[] arguments) {
		StringBuffer sb = new StringBuffer();
		sb.append(targetName).append(".").append(methodName);
		if ((arguments != null) && (arguments.length != 0)) {
			for (int i = 0; i < arguments.length; i++) {
				sb.append(".").append(arguments[i]);
			}
		}
		return sb.toString();
	}
}